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Koc University
MOEMS for Display, Spectroscopy and Imaging Applications
Hakan Urey
Koç University – Istanbul, TURKEY
http://mems.ku.edu.trEPFL Seminars (Neuchatel and Lausanne)
Feb 5-6, 2009
Koc University
Hakan Urey, Koc University-Istanbul
2
Koç University• Private University established by Vehbi Koç Foundation• ~3,500 undergraduate and 400 MS and PhD students.• Established in 1993; College of Engineering in 2001• Among the top Universities in Turkey based on scholarly
research articles and faculty awards
Koc University
Hakan Urey, Koc University-Istanbul
3
Prof. Hakan Ürey (Director)Dr. V.C. Kishore (Post-doc)Sven Holmström
(Researcher) Selim Ölçer (Technician)
Graduate StudentsOnur FerhanogluAslıhan ArslanHuseyin R. SerenErdem ErdenGökhan HatipoğluS. Kutal GökçeDuygu Kutluoğlu (KU-EPFL)Ersin Huseyinoglu
Undergraduate AssistantsUtku BaranErman TimurdoğanÖzge TekinBaran GözcüÖzerk MemişF. Firat Gonen
Research Focus: • Micro-optics, • MEMS/NEMS sensors and actuators, • 2D/3D Display and Imaging Systems
Koc University
Hakan Urey, Koc University-Istanbul
4Outline: OML Research Projects
Brief Overview of:
MOEMS thermal sensor array
3D Displays Not MEMS
Part 1: Electro-Magnetic Actuated Systems:
Pico projectors and 2D MEMS scanner (Lorentz Force)
FR4 scanners for imaging (Moving magnet)
MOEMS biosensors (Thin Ferromagnetic Film)
Part 2: Comb-drive Electrostatic Actuated Systems:
MOEMS Fourier transform spectrometers
Scanned Imaging using MEMS Stages and Microlens Arrays
Koc University
Hakan Urey, Koc University-Istanbul
5
OML Research Projects: MOEMS Thermal Imaging Sensor Array
Bimaterial Legs
1st order
-1st order
0th order
IR
Diffraction Grating
readoutlaser
IR
0 0.2 0.4 0.6 0.8 10
0.2
0.4
0.6
0.8
1
ratio of gap to the wavelength
norm
alized inte
nsitie
s in t
he o
rders
0th
1st
Inte
nsi
ty
Gap / wavelength
Licensed to ASELSAN, TR
JAP 2006; PTL 2008; Sens&Act 2009
Advantages - Eliminates the need for electrical connection- Interferometric sensitivityRecent collaboration with EPFL (Prof. Leblebici)
Koc University
Hakan Urey, Koc University-Istanbul
6
Two-wavelength Interferometry for Extended Range Imaging with Grating Interferometry
λ1
λ2
λ1 & λ2
PD2
PD1
g
O. Ferhanoglu, F. Toy, H. Urey, PTL 2007
Unambigious detectionFull range
Koc University
Hakan Urey, Koc University-Istanbul
7
RB
G
Multi-viewer 3D display technology
Sponsors: TUBITAK; FP6 3DTV
Novel 3D display technology Scanning LED Array on FR4 platform
Sponsor: EC FP7-STREPHELIUM3D
OML Research Projects:3D Display Development Projects
Light engine module of the 3D display system
Koc University
EM Actuated Devices
MEMS Scanners Display
FR4 Scanners Imaging
Ni Cantilever Resonators Biosensor
Koc University
Hakan Urey, Koc University-Istanbul
9Needs a MEMS Scanner
• Case for a scanning mirror & laser light– Together they address all the critical properties
• Small size• Low power• Bright
Single Mirrorscanner
Imageplane
Light source
Koc University
Hakan Urey, Koc University-Istanbul
10Microvision PicoP – MEMS Inside
Integrated Photonics Module (IPM)Including 2D MEMS scanner and
modulated RGB Laser diodes
CES2007
Microvision Inc.
2D MEMS Scanner
CES2008
Koc University
Hakan Urey, Koc University-Istanbul
11
2D MEMS Scanner with Single Coil Magnetic Actuation
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Vertical Scan Flexures (60 Hz)
Horizontal Scan Flexures (20 KHz) Portion of 2D Raster Pattern
for SVGA Display
• Coil current carries excitation signals for both axis:
(60Hz sawtooth + 20KHz sine)
Drive coil
Koc University
Hakan Urey, Koc University-Istanbul
12Microfabrication
• 300um Silicon wafer• Structure formed with DRIE• Front Side:
– Electroplated multi-turn coils – PZR sensors on both flexures– Al mirror
• Backside KOH etched to reduce weight
Integrated PZR Angle Sensor Packaged Device (no vacuum)Includes magnet under Si die
Si Die
R. Sprague et al Proc. SPIE Vol. 5721, pp. 1-13 (2005); Urey et al, Optical MEMS 2006; Yalcinkaya et al, JMEMS (2006)
Koc University
Hakan Urey, Koc University-Istanbul
13
Summary: MEMS Scanner Performance Comparison
SXGA(1280x1024)
0 5000 10000 15000 20000 25000 30000 35000
op
tD (
de
g.m
m)
-
Frequency(Hz)
DickensheetsMiyajima (99)Hofmann (99)
Schweizer (2000)
Lakner(99)Schenk(
Thesis,2000Schenk(2000)Type 1
Wine (2000)Nomad Spec.Urey (steel) (2002) Schenk(2000
QVGA(320x240)
VGA(640x480)
SVGA(800x600)
16
Dickensheets (97)
Miyajima (2004)Torashima (2004)
Schweizer (2000)
Schenk(2001)
Schenk(2000) Wine (2000)
Ko (2004)Urey (2002)
Microvision NOMAD
Steelscanner
Tani (2004)Hilhol (2004)
Urey (2004)
8
24
32
40
48
56
64
72
80
88
96
104
This Work (2005)
2D BimagneticMEMSScanner
Yalcinkaya, Urey, Montague, Brown, Sprague, JMEMS (2006)
HorizontalResolution
VerticalResolution
Koc University
Hakan Urey, Koc University-Istanbul
14
• Silicon MEMS scanners work great but making really low-cost and low-frequency devices proved to be difficult with Silicon!
“In the middle of difficulty lies great opportunity”
– Albert Einstein
Koc University
FR4 Scanners
Koc University
Hakan Urey, Koc University-Istanbul
16
FR4 as an Opto-Electro-Mechanical Platform
Standard PCB technology Excellent electrical, mechanical, and thermal properties Different structural thicknesses: 130um, 200um, 250um, 300um…1.5mm Highly integrated, flexible, robust, low-cost
FR4
FR4 sandwiched between copper laminates
Koc University
Hakan Urey, Koc University-Istanbul
17
High Degree of Integration on mm/cm-sized FR4 Platform (not
possible with MEMS)
Fresnel lens and curved mirror on FR4 for imaging
LED and waveguide on FR4 (displays / optical interconnects)
LED array and focusing leng on FR4(Module for a 3D display)
Integrated module with optics, IC, optoelectronics, 2 DOF scanning
Koc University
Hakan Urey, Koc University-Istanbul
18
Moving Coil with Lorentz Force Actuation
I
FR4 scanner and coil
Urey et al, PTL 2008
5mm x 5mm
Electrical vias
FR4 substrate
Double-sided Cu coils
Mirror attached on one side
Typically < 200Hz operation
Koc University
Hakan Urey, Koc University-Istanbul
19
FR4 Applications: Imaging with Dynamic Focusing
Moving LD mounted on FR4
LD
LD
75 mm
650 mm
500 um
500 um displacement of the laser diode results in about 600mm displacement of the focused spot position
Can think of as either auto-focus OR x-z scanning device
f = 6 mm
Koc University
Hakan Urey, Koc University-Istanbul
20
FR4 Laser Scanner with Dynamic Focusing Experimental Results -
0
100
200
300
400
500
600
50 150 250 350 450 550 650 750 850 950
Distance from Scanner [mm]
FW
HM
Sp
ot
Siz
e [u
m]
6.5mm6.3mm6.2mm6.1mm6mm6.03mm
As the spot is focused further away, spot size gets bigger, DOF gets longer
500um plunger displacement shifts the beam waist location from 70mm to almost 700mm
Isikman, et al, PTL 2009
Koc University
Hakan Urey, Koc University-Istanbul
21
FR4 and Silicon Technology Comparison for EM Actuators
FR4 Silicon
Fabrication Technology Standard PCB MEMS
Density [kg/m^3] 1860 2300
Density of copper 8960 8960
Young's Modulus [Gpa] 10-20 168
Torsional Modulus [Gpa] 2-5 51
Min Coil Trace Width / Spacing100um
10um
Min Via Hole Size
350um (25um with laser)
Min feature size
100um (drill); 20um laser (5um in 2009)
2um (lithography)
Copper thickness 30um 10um
Number of Coil layers 2 - 20 1
Resistance / Power Low High
difficult
Koc University
Type 3: Thin Film Magnetic Actuatorsand MOEMS Biosensor
Koc University
Hakan Urey, Koc University-Istanbul
23
Understanding Soft Magnetic Thin-Film Actuators
•FACT: Unlike thick magnetic films, force can be attractive or repulsive.•WHY? Magnetization vector remains in-plane due to strong shape anisotropy and the whole structure rotates instead of magnetization•FACT: Unlike permanent magnets, force is NOT bidirectional•WHY? Changing current direction, rotates both H and M vectors 180degrees, thus force direction remains the same
Push region Pull region
Torque M H┴
Where M max (Hr, Msat)
Koc University
Hakan Urey, Koc University-Istanbul
24
Modeling Soft Magnetic Thin Film as Array of Permanent Magnets
Isikman et al, JSTQE 2007
Isikman, et al, IEEE J. Magnetism (accepted) about dynamics & hysteresis modeling
Thin magnetic film in external magnetic field
Integrated planar coil
Attractive to use magnetic thin films such as Ni or NiFe as structural MEMS/NEMS layer.
Equivalent system
TNET
FNET
Mirror assumed rigid
Koc University
The magnetic layer is modeled as
an array of permanent magnets:
New Actuator Model for High-Permeability Thin Film Actuators
Isikman et al, IEEE JSTQE 2007
NNN
NNN
HtWMF
HtWMF
'
111
1
1
'1
N
iiiNET FFF
cos)1)(( ' LNFFT NNN
N
iiNET TT
2
Force Calculation:
Torque Calculation:Equivalent system
TNET
FNET
Mirror assumed rigid
Koc University
New Model Validation for Permalloy Thin Films
y=9y=-4
Model can handle:
•Non-uniform fields
•Saturated/unsaturated film
Isikman, Ergeneman, Yalcinkaya, Urey, IEEE JSTQE 2007
Koc University
Hakan Urey, Koc University-Istanbul
27
Target Molecule
Gold
Probe Molecule
Target Binding
Chip
Chip
Chip Chip
Ch ip Chip Chip SiNX
MEMS Chemical/Bio Sensors
• Chemical to Mechanical Free Energy Transduction
• Universal Platform for Any Chemical Reaction
• Mass loading -Resonance Frequency
• Label Free
• Multiplexing
Interactions• Steric• Electrostatic• van der Waals
Before Reaction
After Reaction
Thundat et al. (ORNL), APL’94; Chen et al.,” J. Appl. Phys (1995).
Koc University
Hakan Urey, Koc University-Istanbul
28Biosensor Research at Koc University
Blood sample
Disposable MEMS Chip Reflector
for optical readout
Functionalized cantilever array(parallel operation)
EM actuation coil / Optoelectronics module for readout
Electronics control/readout
Dynamic Mode Actuation: Use magnetic material as structural material instead of Si or SiNDetection: Optical using integrated grating interferometer
TÜBİTAK
Protein-ligand interaction changes the dynamics of Micro/nano cantilevers
Koc University
Hakan Urey, Koc University-Istanbul
29Diffraction Grating Readout
Gap /
• Grating pattern can be on the moving or fixed structure
• Extremely sensitive: can detect mechanical deflections on the order of 2x10-4A/Hz½ at 20KHz. Used for AFM and acoustic sensing; IR sensing;
Ferhanoglu, Toy, and Urey, PTL 2007
Degertekin, et.al. JSTQE 2004 (Georgia Tech)
0th1st
3rd
-1st
-3rd
gapGrating
Si substrate
PD0PD1
Electro-coil
NiFe cantilever
Koc University
Hakan Urey, Koc University-Istanbul
30Simple Microfabrication
• Magnetic actuation of Nickel thin film (~1um thick)
Silicon
Au + Ni
PR
Si (doped)
Photoresist
Mask
Ni or NiFe
Remove PR
Isotropic Silicon Etching
~100um5-10um
In collaboration with Profs. E. Alaca and H. Kavakli at Koc University
Koc University
Hakan Urey, Koc University-Istanbul
31
Fabricated Cantilevers with Diffraction Gratings(Fabricated in our clean room)
They all work despite not so great surface quality Thanks to AC-coupled detection, and bias/noise rejection
of diffraction grating readout,
Ozturk et al, PTL 2008
Koc University
Hakan Urey, Koc University-Istanbul
32Bio-detection Results
Resonance frequency shift of a cantilever due the attachment of human kappa opioid receptors (hKOR) to the Au surface.
180Hz shift 85pg of mass
Ozturk et al, PTL 2008
SENSITIVITY is GOOD, future work will focus on improving SPECIFICITY
Koc University
Comb Actuated Devices:
1. Fourier Transform Spectrometer2. MEMS Stages with Microlens
arrays
Koc University
Hakan Urey, Koc University-Istanbul
34Portable Mid/Far IR Spectroscopy
• FTIR spectroscopy is the common choice due to single detector operation
• Requirements for compact FTIR Spectrometers– Translating mirrors with long travel
range– Precision scanning – Real-time operation– Large clear aperture
• Approaches– Michelson interferometer– Lamellar grating interferometer
(eliminates beam splitter and reference mirror, more compact)
Manzardo, Opt. Let., 29, 1437–1439, 2004.
Schenk, Optical MEMS 2005Kenda, Proc. of SPIE, 6186, 618609, 2006.
Ataman, JMM, 16, 2517-2523, 2006
Koc Univ., TR
U. Neuchatel, CH
Faunhofer IPMS, DE
Koc University
Hakan Urey, Koc University-Istanbul
35FTS : Lamellar Grating Interferometer Based
4d N
a
/a
/a
2 4
coscenter
dI A
0
0.2
0.4
0.6
0.8
1
0 0.5 1 1.5 2
Faz Derinliği (d /)
Işık
şid
deti
Grating Depth (d/)
Inte
nsit
y
0
0.2
0.4
0.6
0.8
1
0 0.5 1 1.5 2
Faz Derinliği (d /)
Işık
şid
deti
Grating Depth (d/)
Inte
nsit
y
Monochromatic Light
Grating Side View
FourierTransform
0 /
DC
Spectrum
Koc University
Hakan Urey, Koc University-Istanbul
36MEMS Grating: Features
x
yz 1
1
2
2
3
4
4
4
4
1
2
3
4
Fixed Fingers
Movable Fingers
Rigid Backbone
Folded Flexures
Size 2.7mmx2.65mmFlexure Length 1.2mmFlexure Width 10-5m# of Folds 4Backbone Width 250mFinger Width 70mFinger Gap 5mFinger Length 1.2mmDiffraction angle 7mrad (@635nm)
Dimensions of the Device
o Comb fingers function as grating, actuators and position feedback
o Large clear aperture and good optical efficiencyo Simple fabrication process
Technology Licensed to Fraunhofer IPMS
Koc University
Hakan Urey, Koc University-Istanbul
37
400 500 600 700 800 900 10000
0.2
0.4
0.6
0.8
1
Wavelength (nm)
No
rm
alized
In
ten
sity
FTS MeasuementReference Measurement
Spectral Measurements
FTS Measurement: =638.8nm, FWHM= 24 nm
Commercial visible spectrometer =638.8nm; FWHM =1.5 nm
FTS Theory: = 2.3nmfor 30um deflection
Measured Narrowband Spectrum
Ataman, Urey, Wolter, J. Micromechanics and Microengineering, Vol. 16, p. 2517, 2006
Photodetector Signal Measured Broadband Spectrum
Koc University
Hakan Urey, Koc University-Istanbul
38Currrent and Future Work in this area
• MEMFIS Project “Ultrasmall MEMS FT-IR Spectrometer“ started in 2008 (funded by EC-FP7)
• Develop a MEMS based compact FTS for mid and long IR applications
www.memfis-project.eu
Koc University
Scanned Imaging using MEMS Stages and Microlens Arrays
(Microfabrication 2nd run planned at EPFL clean rooms)
Koc University
Hakan Urey, Koc University-Istanbul
40Scanning with MLAs
A. Akatay, C. Ataman, H.Urey, Optics Letters, 31 (19), 2861-2863, 2006.
laser
PSLMLA1 DMLA
FL
• Beam steering is possible by laterally moving a collimating lens wrt focusing lens • Using microlens arrays (MLA) allows for large angle steering with small lateral displacements • However, beam steering with MLA has a fundamental diffraction related problem!
•Can address only discrete angles set by period of MLA
• Our group showed that moving PSL and MLA1 in SYNC allows for continuous addressing!
Moving MLA only
Moving PSL and MLA together
Koc University
Hakan Urey, Koc University-Istanbul
41
Demonstrated Continuous Scanning with Microlens Arrays
(a)
(b)
a.u.
/ d(c)
-4 -3 -2 -1 0 1 2 3 40
50
100
150
200
(=0.532m) and the beam size is around 600m pitch (d) = 200m
Can fit ~150 spots with continuous addressing
>1000 resolvable spots using Higher f# lenses and 2mm clear aperture
~40 discrete addressable spotsUsing 650um clear aperture
*Akatay, Ataman, Urey, Optics Letters, 2006
*Akatay, Urey, Optics Express, 2007
Koc University
Hakan Urey, Koc University-Istanbul
42MOS: Fabricated Devices
• Fabricated at Chalmers University
• 20 m and 50 m thick (SOI)• Fabrication process similar to
1st gen. MEMS spectrometer
Microscope Pictures
SEM Pictures
Koc University
Hakan Urey, Koc University-Istanbul
43Fabricated MLAs
• Replicated on 20 m thick Cytop layer
• 100% Fill Factor• 75m pitch size• f/4 (300m f. length)• Embossed using KS SB6
Wafer Bonder
• New fab run planned at EPFL (Feb-April 2009)
Hedsten et. al., MME 2008(Koc and Chalmers collaboration)
Koc University
Hakan Urey, Koc University-Istanbul
44Summary Remarks
• MOEMS (i.e., moving micromechanical structures combined with laser light sources and micro-optics) is a powerful technology and enables a number of applications:
– Thermal sensors, 2D and 3D Displays, Bio-sensors, Spectroscopy, and Imaging are some of the applications explored at Koc U.
• 3-types of EM actuators are discussed: moving coil, moving-magnet, and soft-magnetic film. Selection depends on application.
• Best reported MEMS Scanner performance is achieved using bi-magnetic Lorentz force actuator. Suitable for pico-projector applications.
• FR4 mechanical properties and integration with optics not explored before:
– offers low-cost and high degree of integration
– good choice for many applications: 3D displays, FTS, advanced imaging with dynamic focusing, etc.
• Comb-actuated in-plane and out-of-plane moving platforms are utilized for high-performance FTS and beam steering applications
– Comb actuation provide compact form-factor and low-power.
• Mechanical coupling provides an interesting way to actuate, can be used both for EM and ES actuated MEMS devices.
Koc University
Hakan Urey, Koc University-Istanbul
45Acknowledgments
All the past and current students and researchers at OML
Funding Resources:• Microvision Inc. (USA)• FP6 Projects: NEMO, 3DTV, MC2ACCESS,
MINOS-Euronet• FP7 STREP Projects: MEMFIS, HELIUM3D• ASELSAN Inc. (Turkey)• Fraunhofer-IPMS (Germany)• TÜBİTAK (Scientific and Technical Research
Council of Turkey)• TÜBA-Distinguished Young Scientist Award,
Turkey• NSF (USA)
MEMS / Micro-Optics / 3D Displays• Post-doctoral research positions
available• PhD positions available